A private initiative to end the Israeli-Palestinian conflict has run into trouble just hours before the plan was due to be launched at a signing ceremony in Geneva.

Four prominent Palestinians who negotiated draft peace accords with their Israeli counterparts have canceled their participation at the official launch Monday in Switzerland.

Three of them are members of the Palestinian Cabinet, and the fourth is a representative in the Palestinian parliament.

The Palestinian negotiators announced they were pulling out, after Palestinian President Yasser Arafat refused to offer his written support for the informal plan, known as the Geneva Accords.

The announcement also followed an incident last week in which masked Palestinian gunmen opened fire on the house of former Palestinian Cabinet Minister Yasser Abed Rabbo, a key architect of the agreement.

One of the strongest points of contention is that, under the plan, the Palestinians would effectively agree to give up the right of return for millions of refugees to areas that are now part of Israel.

In a further sign of opposition, about 200 Palestinians in the Gaza Strip attacked another group of Palestinian participants traveling Sunday to Geneva for the signing ceremony.

The angry demonstration was one of several held in Gaza this month that have raised doubts about the level of Palestinian public and official support for the document.

Mr. Arafat has given his tacit approval to the Geneva Accords, but there is strong opposition to the plan from within his own Fatah party, the dominant faction of the Palestine Liberation Organization, the PLO.

The Palestinian Islamic groups, Hamas, and the Islamic Jihad, which frequently carry out suicide bombings and other terror attacks, have also denounced the initiative.

Both organizations oppose a two-state solution to the Israeli-Palestinian conflict, and call for the destruction of Israel.

From the Israeli side, Prime Minister Ariel Sharon has stated his opposition to the plan, saying that only his government has the right to negotiate on behalf of the Jewish state.

The chief Israeli architect of the accords is Yossi Beilin, a former Israeli Cabinet minister.

He says it was necessary to provide a model for peace-making, because Mr. Sharon's government has no intention of reaching a negotiated settlement of the conflict with the Palestinians.

Mr. Beilin conceded that the pullout of the four Palestinian participants is a blow to the project, but he remained hopeful that the initiative could still succeed.